525 build thread

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Potato Cakes

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The ceiling control is an odd bird. Turning up the ceiling control will cause and increase in level that will in turn feed the compression circuit. Start with the ceiling control all the way up and then feed it signal. Then adjust the threshold to see if you can hear gain reduction. Also, just to be sure, make sure the circuit is engaged and the compressor is engaged (I've neglected to do this before).

Is this the first or second revision? Do you have a known working VCR2N?

Thanks!

Paul
 

duantro

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Potato Cakes said:
The ceiling control is an odd bird. Turning up the ceiling control will cause and increase in level that will in turn feed the compression circuit. Start with the ceiling control all the way up and then feed it signal. Then adjust the threshold to see if you can hear gain reduction. Also, just to be sure, make sure the circuit is engaged and the compressor is engaged (I've neglected to do this before).

Is this the first or second revision? Do you have a known working VCR2N?

Thanks!

Paul
Thanks for the comments. It’s a first version. I do have 3 others that work. Maybe I’ll swap out the vcr2n and see if that does anything.
The amplifier portion of the ceiling control is working as it gets louder, but doesn’t compress. Switches are engaged (in and compress)  I know it’s got to be something I’m overlooking.
 

Potato Cakes

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I have four of the first versions as well. One thing that I kept coming across is on some of the units, the wire I was using kept breaking from it's connections in different spots as they were started from another person as well (Peter's prototypes to be exact).

Thanks!

Paul
 

duantro

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Yeah, the person I got this from used solid core wire that kept breaking also, so I replaced all of the wires. We are truly glutton's for punishment trying to resurrect someones projects.
Edit: tried with a different vcr2n and still no compression, only volume boost
 

duantro

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I've been staring at the schematics trying to figure out how this side chain works. It makes it pretty hard to trouble shoot without this knowlege. The comp and limit switches seem to be connecting the circuit and showing changes on the meter, but I can't deduct where the gain reduction should be attenuating.  I'm also noticing about a 30% volume output, even with the output volume turned all the way down. I've searched for solder bridges and don't see anything ...
 

Potato Cakes

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Did you make all the board corrections since you're using a first version? I believe there are some besides the fixes for the attack control. I also remember having some transformers wired incorrectly when I first made mine. The volume should be working correctly if you have the right value for the potentiometer and it is free of connection errors. I had to use the schematic and do a fair amount of continuity tests when I was troubleshooting. It always came down to a misplaced/bad/no connection with at least one solder bridge I think.

Thanks!

Paul
 

duantro

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Yes, I think I have all of the fixes done. The Attack mod, the Meter ground mod, The termination blunder mod, etc... I didn't have to do the A4 mod as the previous builder of this lot lost the A4 board. Very generous member Ivan was kind enough to send me one of his version 2 A4 boards, that I retro fitted. This was quite a task as V2 A4 boards had lots more of the passive input components on it.  I had to jumper those, as I already had them installed on the main board.
So I've just got to find where this 30% signal is making it to the output. I'm guessing that this is where the compression isn't making it back in the circuit somewhere
 

duantro

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Potato Cakes said:
Did you socket your A4 boards? I am guessing you swapped op amp boards out of habit.

Thanks!

Paul
On my other v1 builds I soldered them in. The last one that I’m trouble shooting, I socketed it in. Mainly because it is a v2 A4 board, and I wasn’t sure if it’d be an issue.
 

Potato Cakes

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AudioCommand said:
Hey guy's,

any one have the calibration guid for me...?


Thank's Dom

It should be attached somewhere in the this thread. It's just the original API 525  calibration guide. The controls and trimmer designation match up with Peter's design. There isn't another guide written for the ACL.

Thanks!

Paul
 

AudioCommand

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I'm dominic from germany.

I build the lazpro 525 V2 and have them since years... and now I whant to finish them.

But my problem is that I lost all files with a hd crash!

I'm realy thankfull for posting the calibration files! But I need more infos and all files/links in the building trades are death...

Any one can send me his info pack with schematics, overlay, bom, and the calibration guid...

My email.....dominicmaierhn@gmail.com

That's realy helpfull!

Thank's for your time

Dominic
 

duantro

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Can anyone enlighten me on how the sidechain works here? I'm still trying to get the unit I got from another member resurrected. The meter shows compression, but output isn't attenuating, audio just gets louder as I increase the more/ less switch. I've ran all new wiring, and have checked all of it, as well as the components many many times.
 

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shabtek

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Looks like a bridge rectifier after the sidechain XFMR . Positive v drives meter neg is cv to vcr2n in yellow.

Check diode orientation.
Maybe isolate that branch going over to the variable release thing.

OT :Seems like a weird way to switch 2 release time resistors either 1M or 24M
—what goes on over there in the bottom right?  If there is a really big peak those transistors turn and ? The release time?
 

duantro

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Thanks Shabtek. I must have kept overlooking that yellow line back to the vcr2n. All of the diode orientation are correct. I think I have a spare vcr2n to try and see if that works.
 

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